Y chromosome mosaicism in the gonads, but not in the blood, of a girl with the Turner phenotype and virilized external genitalia.

We describe a girl with virilized external genitalia and phenotypic features of Turner syndrome whose blood karyotype is 45,X. The presence of dysgenetic testicular tissue was confirmed by pathology. Using PCR and primers for the distal long arm, centromere and short arm of the Y chromosome, Y chromosome material was detected in her gonads but not in blood.